Implantable cardiac electrotherapy leads are electrically coupled to implantable cardiac electrotherapy devices such as pacemakers, defibrillators or implantable cardioverter defibrillators (“ICD”). Leads connecting such devices with the heart may be used for pacing or for sensing electrical signals produced by the heart or for both pacing and sensing in which case a single lead serves as a bi-directional pulse transmission link between the device and the heart. The lead typically includes a distal end portion for carrying a tip electrode and a ring electrode. The lead may also carry one or more cardioverting and/or defibrillating electrodes proximal of the ring electrode.
Various lead types for different placement approaches have been developed. For example, an endocardial type lead is one that is inserted into a vein and guided therethrough to a target location, for example, in one or both of the chambers of the right side of the heart or within one of the veins of the coronary sinus region of the heart for left side stimulation and/or sensing. The distal end portion of an endocardial lead may carry a helical, screw-in tip element, electrically active or inactive, and/or outwardly projecting tines or nubs and/or a sinuous shape for anchoring the lead.
There are factors, however, which warrant alternatives to a transvenous lead implant approach. These factors include coronary sinus and/or coronary venous obstructions. Furthermore, the coronary veins dictate the implant location of the electrode, which can make optimal left side lead placement impossible and may cause long and unpredictable implant times. In addition, approximately 10% of the patient population is unable to receive this type of lead due to vasculature anomalies. In such cases, epicardial or myocardial type leads may be used. Such leads are attached directly to the epicardium using sutures or another fixation mechanism such as a helical screw-in electrode that engages the myocardium. Myocardial leads typically are used for temporary pacing or for permanent pacing following open-heart surgery.
Conventional approaches to the placement of epicardial leads usually involve thoracotomies or sternotiomies. Such placement techniques have disadvantages including the relatively large incisions needed to gain access to the thoracic cavity and to the heart; the difficulty of quickly and easily attaching the lead; the high rate of patient morbidity, trauma and pain; the tendency to require longer in-patient recovery times; and the unattractiveness of the scars left by the procedure.
To mitigate these disadvantages, minimally invasive lead placement techniques have been developed for placing a myocardial lead on the surface of the heart via a small, finger size opening in the chest. Such techniques may include the use of a fiber optics video camera of the type commonly used in other thoracic surgeries (for example, lung biopsies and other thoracic cavity and cardiac procedures) for visually imaging, and thereby aiding, the lead placement procedure. These minimally-invasive lead placement techniques allow for faster, safer and easier myocardial lead placements with significantly less morbidity, trauma and pain to the patient.
It is not unheard of for an implanted lead to require extraction due to shifting of the lead, lead failure, improper implantation, changes in the electrical characteristics of the implantation site, etc. As with all types of implantable leads, including leads implanted via minimally-invasive techniques, extraction of an implanted lead can be risky for the patient and difficult due to the configuration of the lead and/or tissue ingrowth about the lead.
There is a need in the art for a lead that facilitates the accurate placement and subsequent anchoring thereof within the intrapericardial space while providing for a reduced level of difficulty and risk during potential future extraction of the lead. There is also a need in the art for method of intrapericardially implanting and extracting such a lead.